1. Field of the Invention
The invention relates to substrate handling systems, and more particularly, to systems using robots to transport substrates between different locations.
2. Description of Related Art
During integrated chip manufacture and other industrial applications, substrates such as semiconductor wafers undergo numerous processing steps. Typically, these steps take place in dedicated processing stations remotely situated from each other and from the storage containers or cassettes used to hold the substrates. In integrated chip manufacture, the semiconductor wafers from which the chips are fabricated need to be contained in a carefully controlled environment in which temperature, humidity, and contaminant level, among other factors, need to be carefully controlled. Robots are often deployed to transport the wafers between processing stations, or to retrieve and return the wafers to the storage cassettes before and after processing.
One prior art arrangement for handling semiconductor substrates is shown in FIG. 1, wherein a robot arm 10 is used to transport the substrates (not shown) between a bank of processing stations 12. Robot arm 10 has three arm links 14, 16 and 18 mounted in a base 19. Proximalmost link 14 is rotatably mounted at its proximal end to base 20, and links 16 and 18 are similarly mounted such that each succeeding link is rotatably mounted to the distalmost end of the preceding link. Rotation of links 14, 16 and 18 is mechanically coupled, using suitable linkages such as belts and pulleys (not shown), such that the distal end of distalmost link 18 can be extended or retracted relative to base 20. A first motor (not shown) motivates this motion. The distal end of distalmost link 18 supports an end effector 22 which may be mounted for independent motion, using a second motor (not shown), such that yaw motion of the end effector can be achieved.
To laterally extend the reach of robot arm 10, base 20 is mounted for translation in the x direction, on a track 24. In this manner, robot arm 10, and end effector 22 in particular, can be moved along the x direction to reach an increased number of processing stations 12. A third motor (not shown) is used to effect this translation.
The above prior art arrangement suffers from several disadvantages. First, valuable space is wasted by track 24 and the supporting components required to translate robot arm 10 in the x direction, space generally delineated by the dashed line 26 in FIG. 1. Second, motion along track 24 generates friction, which in turn generates particles which contaminate the "clean room" environment required for semiconductor processing.